Add fallback dupe detect to make transition less painful.
Add fallback dupe detect to make transition less painful.

Will do time + filename matching as a backup when there are photos with
no original version hash. When a dupe is detected, a hash calculation is
scheduled. This ensures that we will have hashes in there at some point.

dkoeb/f-spot,NguyenMatthieu/f-spot,dkoeb/f-spot,nathansamson/F-Spot-Album-Exporter,mono/f-spot,GNOME/f-spot,mans0954/f-spot,Yetangitu/f-spot,GNOME/f-spot,Sanva/f-spot,mans0954/f-spot,dkoeb/f-spot,nathansamson/F-Spot-Album-Exporter,Sanva/f-spot,mans0954/f-spot,Yetangitu/f-spot,mono/f-spot,mono/f-spot,GNOME/f-spot,Sanva/f-spot,dkoeb/f-spot,mans0954/f-spot,dkoeb/f-spot,nathansamson/F-Spot-Album-Exporter,Yetangitu/f-spot,mono/f-spot,NguyenMatthieu/f-spot,mono/f-spot,NguyenMatthieu/f-spot,Yetangitu/f-spot,Yetangitu/f-spot,mans0954/f-spot,NguyenMatthieu/f-spot,nathansamson/F-Spot-Album-Exporter,GNOME/f-spot,GNOME/f-spot,mans0954/f-spot,mono/f-spot,Sanva/f-spot,dkoeb/f-spot,NguyenMatthieu/f-spot,Sanva/f-spot